The invention relates to a control system for the control and distribution of power to the wheels of a motor vehicle, such as an agricultural tractor.
A known control system for the control and distribution of power to the wheels of a vehicle with all-wheel drive is described in German Patent No. DE 34 08 991 C2. In order to reduce the radius of the turning circle this control system includes a shift arrangement which automatically raises the wheel speed of the front wheels upon exceeding a predetermined steering angle of the front wheels so that their circumferential speed is two to three times as high as that of the rear wheels. Furthermore, at high vehicle speeds the all-wheel drive is automatically shifted to a two-wheel drive. The abrupt changes in the distribution of the power supply to the individual wheels that occur in this shift, however, impairs the stability of steering and safety.
To improve the steering stability and avoid skidding of the vehicle, German Patent No. DE 36 26 025 C2 proposes to control the distribution of the power supply to the front and rear wheels when slippage occurs. For this purpose the vehicle speed, the circumferential speed of the wheels and the turning circle radius are detected. The latter corresponds to the steering angle of the front wheels. See also, for example, German patent No. DE 34 27 725 C2. These values are used to generate a control signal corresponding to the desired drive torque which is used to control a distribution clutch in order to apply the desired drive torque to the rear wheels. However, this drive arrangement does not permit equalizing slippage that can occur between the wheels of an axle.